The present invention relates generally to a manner by which to reduce, or otherwise alter, the resolution of a block-based digital image. More particularly, the present invention relates to apparatus, and an associated method, by which to operate upon the block-based digital image such that reduction of the image is effectuated through a matrix multiplication using a multiplier that exhibits symmetry. Reduction of the resolution of the image is readily implementable, and said reduction is effectuated with a reduced complexity relative to conventional manners by which to reduce the resolution of the image. And, the resolution reduction produces an image that exhibits a lessened aliasing than conventional manners used to reduce the resolution of a digital image.
The use of a communication system through which to communicate data is a pervasive part of much of modern society. Many different types of communication systems have been developed, implemented, and used to effectuate communication of data pursuant to a communication service.
Generally, a communication system is formed of a sending station and a receiving station interconnected by a communication channel. The sending and receiving stations are positioned remote from one another and, by interconnecting the sending and receiving stations by way of the communication channel, data originated at the sending station is able to be communicated to the remotely-positioned receiving station. A communication station that includes both a sending station and a receiving station permits two-way communication of data, i.e., data originated at the communication station can be communicated elsewhere, and data originated elsewhere can be detected at the communication station.
New types of communication systems have been proposed, developed, and, in some instances, also implemented, that make use of advancements in communication technologies. For instance, communication systems have been proposed for the communication of digital video data formed of digital images. The digital image is formed, for instance, of video frames, and video images, utilized during video conferencing are exemplary of applications that make use of digital images.
A radio communication system is a communication system in which the communication channel is formed of a radio channel. Because a radio channel is employed, a conventional, fixed wireline connection between the sending and receiving station upon which to define the communication channel is obviated. Radio communication systems can be utilized to effectuate the communication of a digital image, or sequences of digital images, between the sending and receiving stations of a radio communication system. Communication of a digital image is a data-intensive procedure as a digital image is formed of a significant amount of data. The data forming the digital image is represented, in part, by dimensions that define the resolution of the digital image.
A digital image stored at one resolution might need to be processed at a different resolution. For example, a high-resolution image might have to be displayed upon a device that is capable of displaying the image at only a lower resolution. A conversion of the image to the lower resolution can be performed at a display device, such as a display device positioned at the receiving station to which the digital image is communicated by the sending station. That is, the conversion can be performed at the receiving station by decoding the image at the stored resolution and then scaling the decoded version in the pixel domain. This type of conversion procedure is typical of procedures conventionally utilized by image viewers associated with conventional personal computers, including web browsers used in conjunction with operations by way of the World Wide Web (WWW).
This type of conversion operation, however, necessitates that the decoding device be capable of processing the image at the stored resolution. That is, the decoding device must have sufficient amounts of memory capacity and sufficient levels of processing capability. This type of procedure also ignores the relatively greater cost of obtaining the image at the stored resolution compared to the displayed resolution.
The digital image might be communicated in a communication system in which a receiving station at which the digital image is to be displayed is of limited memory capacity or processing capability. For instance, mobile communication systems, both those under development, as well as systems that are already installed, make use of mobile stations that are, generally, of limited memory capacity and limited processing capability when compared to fixed-point stations. Increasingly, communication services that are to be effectuated include communication services in which digital images are communicated to the mobile station. Because of the limited memory capacity and processing capability of many mobile stations, conventional manners by which to reduce the resolution of a digital image cannot practically be performed at the mobile station. That is, a mobile station may not be capable of decoding an image stored at a resolution considered xe2x80x9cnormalxe2x80x9d on a conventional personal computer, or even of decoding images generated by other mobile stations. Additionally, costs associated with transmitting a digital image upon a radio link may be significant due to the large amount of data associated with that digital image. Reducing the dimensions of an image prior to its transmission upon the radio link would reduce the amount of data associated with it, thereby providing a cost advantage.
Different mobile stations operable in a mobile communication system, however, might well have different memory capacities and processing capabilities. A sending station located at the network infrastructure of the mobile communications system may be unaware of the capacities and capabilities of the mobile stations to which data is to be communicated. While it is possible for the operator of the network infrastructure to reduce the resolution of an image by decoding it and reducing the resolution in the pixel domain, then re-encoding the image, this is an unnecessarily complex method, because the operator does not intend to view the image; the operator, and the network infrastructure controlled by the operator, act simply as a conduit of the image.
As many digital images might well have to be converted to lower resolution images, the cost of performing a single conversion is incurred repeatedly by the operator, so that in total, a large amount of processing might have to be performed. A manner is, therefore, required by which to provide an efficient method by which to reduce the resolution of a digital image.
It is in light of this background information, related to the communication of digital images in a communication system, that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides apparatus, and an associated method, by which to reduce, or otherwise alter, a block-based digital image.
Through operation of an embodiment of the present invention, a manner is provided by which to operate upon the block-based digital image such that reduction of the resolution of the image is effectuated through a matrix multiplication using a matrix multiplier that exhibits symmetry. Reduction of the resolution of the image is readily implementable and the reduction is performed with lessened levels of complexity in contrast to conventional manners by which to reduce the resolution of the digital image.
Because the matrix multiplication is performed utilizing a symmetric matrix multiplier, reduced amounts of temporary, e.g., intermediate-stage, data is generated, thereby reducing complexity of the reduction operations. Additionally, low pass, DCT (discrete cosine transform) coefficients are utilized without the need for filtering, again facilitating a reduction in the complexity of the operations required to reduce the resolution of the digital image.
As a result of the reduced complexity of operations, a reduced-resolution image is formed more quickly than conventional manners by which to reduce the resolution of the digital image.
In one aspect of the present invention, a manner by which to reduce the image resolution of a digital image is provided. The digital image is a compressed image, utilizing a block-based transform, such as a DCT (discrete cosine transform), wherein the reduction is by a factor that is a power of two. A transform, such as the aforementioned discrete cosine transform, is utilized in conventional image compression standards, such as the JPEG standard.
Improved efficiency of resolution-reduction operations occurs because less processing time is required to perform the resolution-reduction operation.
In another aspect of the present invention, the block-based digital image is formed of one or more groups of two separate blocks that are provided to separate operational paths of resolution-reduction apparatus. Pre-scaling is performed upon the separate blocks in manners such that a central reduction stage forms a matrix multiplication process wherein a matrix multiplier is utilized. The matrix multiplier is highly symmetric, viz., both rows and columns of the matrix multiplier are divisible into pairs with only one multiplication being required for the pair. In contrast, conventionally, a separate multiplication is required to be performed for each element.
In another aspect of the present invention, dequantization and requantization stages are eliminated and are, instead, merged with pre-scaling and post-scaling stages, respectively. Through this merging of operations, the number of multiplications required to reduce the resolution of the block-based digital image is decreased significantly.
In one implementation, the digital image is reduced in resolution pursuant to effectuation of a communication service with a mobile station, such as a cellular mobile station operable in a cellular-like communication system. The digital image, in compressed form, is provided to the network part of the communication system, at which the resolution of the digital image is reduced, prior to its communication by the network over a radio link to the mobile station. Because the reduction in resolution is performed at the network, the operations otherwise required to be performed at the mobile station are obviated. And, because the reduction in the resolution of the digital image is performed efficiently, processing required at the network to perform the reduction in resolution of the digital image is reduced relative to the processing that would otherwise be required to perform such operation utilizing conventional techniques.
In these and other aspects, apparatus, and an associated method, is provided for a device that operates upon a block-based digital image. The digital image exhibits an initial resolution. The block-based digital image defines at least a first block of a first dimension. The initial resolution of the digital image is selectively reduced to a first-reduced resolution. A prescaler is coupled to receive indications of each block that together define the block-based digital image. The prescaler scales the indications of each block of the block-based digital image to form a first-scaled variant representation of each block of the block-based digital image. A combiner is coupled to receive the scaled variant representative of each block of the block-based digital image. The combiner combines the scaled variant representation of each block together to form a combined representation of the scaled variant representation of each block of the block-based digital image. A reducer is coupled to receive the combined representation formed by the combiner. The reducer reduces the combined representation in resolution to a reduced-resolution representation of the combined representation of the first-reduced resolution.
A more complete appreciation of the present invention and the scope thereof can be obtained from the accompanying drawings which are briefly summarized below, the following detailed description of the presently-preferred embodiments of the invention, and the appended claims.